The kernel of the present invention is a magnetic tunnel junction (MTJ) device, which has, as its core part, a sandwich structure including an insulating barrier layer interposed between two ferromagnetic material layers. Under an external magnetic field or by a pinning effect, the two ferromagnetic layers may have their magnetic moments aligned parallel or anti-parallel with each other, and the magnetic tunnel junction has a significantly different resistance in the parallel state than in the anti-parallel state, which is also called as Tunneling MagnetoResistance (TMR) effect. Magnetic tunnel junctions have been applied in magnetic field sensors and magnetic random access memories. In addition, a phenomenon is observed in the magnetic tunnel junctions that its resistance in the anti-parallel state varies linearly with respect to temperature, which can be used to make temperature sensors.
There are many kinds of existing temperature sensors, including thermocouple temperature sensors, thermistor temperature sensors, platinum resistor temperature sensors, semiconductor temperature sensors, and the like. As an important kind of sensors, the temperature sensors have been widely used in personal life and industrial applications. The existing temperature sensors have their own disadvantages. The thermocouple temperature sensor is not easy to be integrated due to its large size and requiring a cold-end temperature compensation circuit. The resistor-type temperature sensor, for example, a platinum resistor temperature sensor, has a self-heating problem, and its cost is relatively high since platinum is a precious metal, so it is used in a relatively narrow range of applications. The thermistor temperature sensor has a poor linearity, relatively low measurement accuracy, and a narrow measurement range.
The TMR temperature sensor, which has an element of magnetic tunnel junction, almost avoids all the disadvantages of other existing temperature sensors (e.g., cold-end compensation, self-heating, low sensitivity, large size, etc.), and meanwhile it combines the following advantages: (1) high accuracy; (2) high stability; (3) high sensitivity; (4) low load, low power consumption, low heat capacity, and high energy efficiency; (5) integrability; (6) mass production ability and low cost; (7) miniaturization; (8) long lifespan; (9) digitalizability; (10) environment friendliness without pollution; and so on. Therefore, it has a very wide range of applications and is more suitable for temperature detecting and monitoring systems of aeronautics and astronautics spacecrafts and detectors, satellites, spacesuits, and space capsules and simulating chambers, for temperature detecting and monitoring systems of terrestrial ships, movable vehicles, and portable personal communication apparatuses, robot systems, industrial automation systems, many types of products such as automobile and civilian products, and the like.